The present invention relates to a semiconductor device. More particularly, the invention relates to a semiconductor device suitable for use in detecting touch events taking place over a capacitative touch panel, for example.
Touch events occurring over the touch panel (touch screen) are known to be detected using diverse detection methods such as resistive membrane method, optical method, ultrasonic sensing method, and capacitive sensing method (surface type and projection type). Of these methods, the projection type capacitive sensing method is most commonly used for the touch panel attached to smartphones, tablet terminals and the like.
The projection type capacitive sensing method comes in two types: self-capacitance method and mutual capacitance method. The self-capacitance method involves having X-direction touch electrodes and Y-direction touch electrodes arrayed in a grid-like pattern. Sensing growing stray capacitance of each of the touch electrodes detects whether a human fingertip has approached (e.g., see Japanese Unexamined Patent Publication No. 2011-14527).
The mutual capacitance method involves having transmitting electrodes and receiving electrodes arrayed in a grid-like pattern. With pulses input to each of the transmitting electrodes, sensing a change in the signal received by each of the receiving electrodes detects whether the human fingertip has approached (e.g., Japanese Unexamined Patent Application Publication No. 2012-502397).